The present invention relates to circuit board assemblies comprising a main or motherboard and a satellite or daughter board. More particularly, the present invention relates to a circuit board assembly in which an aperture in the main board receives the satellite board, and a hole in the satellite board provides a surface for a solder joint that connects the two boards.
Many electrical applications contain circuit board assemblies in which one circuit board is connected to one or more additional boards. A main board, commonly referred to as a motherboard, can have several satellite or daughter boards connected to it. Typically, the satellite boards are mounted to the main board in a perpendicular arrangement in order to maximize the number of satellite boards that can be connected to the main board.
The connection between the main and satellite boards can be accomplished in a variety of manners. In conventional circuit board assemblies, various modular connectors frequently facilitate the connection. For example, main boards can have modular connectors disposed on their surface. The connector is typically an extra component that is secured to the main board and defines a slot having conductive features that communicate with conductive features on an edge of the satellite board. The assembly is fabricating by pushing the edge of the satellite board into the connector, thereby establishing electrical communication between the two boards.
While the use of modular connectors allows for easy connection between main and satellite boards, they also add expense and difficulty to the manufacturing process. The connectors are frequently plastic components that must be separately manufactured and attached to the main board. Furthermore, the connectors are bulky, making the final main board more difficult to handle, package, and transport.
Alternatives to the modular connectors have been proposed. For example, U.S. Pat. No. 5,484,965 to Woychik for a CIRCUIT BOARD ADAPTED TO RECEIVE A SINGLE IN-LINE PACKAGE MODULE discloses a main board that has an aperture adapted to receive a satellite board. While this arrangement does allow for the elimination of the modular connectors, it does not retain some of the benefits of the connectors. For example, the modular connectors provided a stable connection between the two boards.
The present invention provides a circuit board assembly that defines structural features that allow for improved stability in the connection between two boards.
In one embodiment, the assembly comprises a first circuit board defining an aperture and a second circuit board having an edge. The first circuit board has at least one conductive feature proximate the aperture, and the second circuit board has at least one conductive feature proximate the edge. Each board has at least one circuit trace in electrical communication with its respective conductive feature. The conductive features of the boards are placed in electrical communication with each other by way of the edge of the second board being disposed in the aperture of the first board. This relationship places the circuit traces of the first board in electrical communication with the circuit traces of the second board.
The second board defines a hole proximate the edge. Preferably, the hole extends through the entire thickness of the second board, i.e., from a first side to a second side.
When the edge of the second board is disposed in the aperture of the first board, the hole is positioned near a surface of the main board. As such, the hole is particularly well-suited for receiving a portion of a. solder joint. In a preferred embodiment, the assembly further comprises a solder joint connecting the two boards. Preferably, the solder joint includes a first portion disposed in the hole and second and this portions disposed on the first board. A fourth portion of the solder joint can be disposed within a void region defined by the first board proximate the aperture.
The present invention also provides a method of fabricating a circuit board assembly. In a preferred embodiment, the method comprises providing a first circuit board; creating an aperture in the first circuit board; disposing a first conductive feature on the first circuit board proximate the aperture; providing a second circuit board having an edge, a second conductive feature proximate the edge, and defining a hole proximate the edge; disposing the edge of the second circuit board within the aperture of the first circuit board such that the conductive features of the two boards are in electrical communication with each other; and disposing a solder joint on the first and second circuit boards. Preferably, the hole is a through hole, and the solder joint comprises a first portion disposed on the first circuit board proximate the aperture, a second portion disposed within the hole, and a third portion disposed on the first circuit board proximate the aperture.